Rail flaw detector mechanism



. @ct. 6, 1936. w. M. PERRY 2,056,291

RAIL FLAW DETECTOR MECHANISM Filed Jan. 21, 1933 @j ii'A ii'A' il-A INVENTOR 3 Walter M. Perrg ATTQRNEY Patented Oct. 6, 1936 PATENT OFFICE RAIL FLAW DETECTOR MECHANISM Walter M. Perry, Brooklyn, N. .Y., assignor to Sperry Products, Inc., Brooklyn, N. Y., a corporation of New York Application January 21, 1933, Serial No. 652,827

6 Claims.

This invention relates to rail flaw detector mechanism of the type employed in the Sperry rail flaw detector cars. The system therein em-' ployed consists in passing a heavy current through the rail to establish an electro-magnetic field and detecting any variations in this field due to presence of internal fissures by means of induction coils which are moved through the field thus established to cut the lines of force and induce E. M. F.s. The coils are arranged in opposed pairs in tandem so that first one and then the other of the coils will enter a region of flaw to cut a different number of lines of force, thus generating a differential E. M. F. which may then be amplified and caused to actuate any suitable indicator, such as a recorder.

It has been found, however, that sometimes very large fissures extending across the entire head of the rail, as well as fissures that have cracked out, that is, internal fissures that extend to the very surface, have given weak indications so that occasionally they 1 were not detected.

It is the principal object of my invention to provide a method of and means for detecting such large fissures.

Further objects and advantages of my invention will become apparent in the following detailed description thereof.

30 In the accompanying drawing,

Fig. 1 is a wiring diagram illustrating the principle of my invention and showing one embodiment thereof.

Fig. 2 is a side elevation of a portion of a Sperry rail flaw detector car showing the form of inventiondisclosed in Fig. 1 applied thereto.

Fig. 3 is an enlarged view of the form of-invention shown in Figs. 1 and 2.

Fig. 4 is a portion of awiring diagram illus- Fi s. 5 and 6 are diagrammatic representations of the theory underlying my invention.

Referring to Fig. 2 of the drawing, I hav 4 shown the Sperryrail flawdetectorcar as comprising'a car body l0, only -a portion of which,

the rail, said brushes being carried bya current brushvcarri'age "15 adapted to ride on the rail;

by meanssuch as wheels IS. The current brush carriage may be raised and loweredby means substantially trating a method by which the form of invenl2 and sets of brushes I3, M in engagement with such as piston rods ll attached to pistons operating within fiuid pressure cylinders I8 mounted on the car body so that when fluid pressure is applied the piston rods move outwardly from the cylinders to lower the current brush car- 5 riage Hi. When the fluid pressure is released, said carriage'may be raised to elevated position by means such as cables i9 and springs (not shown).

For detecting flaws there is provided a search 10 unit in the form of a detector carriage 20 mounted on the current brush carriage l5 and adapted to ride on the rails by means such as wheels 2|. A plurality of pairs of induction coils 22, 22' are mounted within the detector 15 carriage 20, said coils being positioned as shown in Figs. 2 and 3 with their axes crosswise of the rail so as to cut the maximum number of lines of force surrounding the rail as the car moves along the tracks. In Figs. 1 and 5 the diagram- 20 matical representation of the coils shows the coils turned at right angles to their actual position in order that the wiring'connections may be shown. It will be seen that on entering a region of flaw the forward coil of the pair of coils 22, which are connected in opposition, will cut a different number of lines of force than is cut by the rear coil, to set up a differential E. M. F. which may be amplified by the amphfying system disclosed in Fig. 1 and caused to operate an indicator, such as a recorder P. The same is true of the second pair of coils 22'. The method of amplifying the differential E. M. F.s set up by the respective pairs of coils is shown in Fi 1 wherein the pair of coils 22 is connected through a rectifier R to a series of amplifying tubes A, A, A", the output of the last tube energizing the pen relay. L to operate pen P. The pair of coils 22' operate through a rectifier R, the output of which also is connected to the input of amplifying tube A at point 30 and this goes through the amplifying system in the same manner as the output of coils 22 toactuate relayLandpenP. I g The spacing of thecoils of each pair with respect to each other, as well as the spacing of the pairs with respect to each other, is such that the output of one set of coils reinforces and extends the output from the other set of coils, to give a.

maximum input .to the amplifying system. With this spacing of coils,- however, it has been foundthat occasionally a very large fissure or one that is completely cr'ackedout, that is, has come to the surface, gave an indication so weak that sometimes it was not picked up. The reason whysuch fissures have sometimes been missed is disclosed in Figs. 5 and 6. In Fig. 5 it will be seen that a small fiaw F causes a very sudden variation V in the electro-magnetic field E in the region of fiaw. So that when the forward coil 01 a pair of induction coils enters this region there is a very sharp change in the number of lines of force which it cuts. Thus, a substantial differential E. M. F. is generated which after being amplified is sufficient to operate an indicator. In the case of a very large fissure F or one that has actually cracked out, the result is as shown in Fig. 6, namely, a very gradual distortion V of the electro-magnetic field extending on both sides of the fissure to a considerable distance so that the forward coil of a pair of induction coils arranged in tandem is cutting only a very slightly different number of lines of force than the rear coil, and hence the difierential E. M. F. generated is so slight that even after being amplified it is not sufficient to operate the indicating mechanism.

My invention provides a remedy for this condition which is based on the general principle of utilizing a construction which is not subject to a small diiferential as are the pairs of coils 22, 22' because of their necessarily close spacing. For this purpose I may provide several forms of my invention, one of which is shown in Figs. 1, 2 and 3. In this form I provide a pair of coils 22" similar to the pairs of coils 22 and 22 and similarly positioned with their axes across the rail so as to cut the lines of force, but of greater inductive capacity and mounted on the detector carriage 20 so as to provide a much larger spacing between the coils 22" than between the coils of pairs 22 or 22'. Thus, I have shown the coils 22" mounted one at one end of the detector carriage and the other at the opposite end. This large spacing between the coils. 22" means that even though there is a gradual variation V' of the electro-magnetic field there will be a sumcient differential E. M. F. which upon amplification will energize relay L to operate pen P. This result is further emphasized by the greater inductive capacity of coils 22". I have shown the output of the pair of coils 22" as connected to the input of a rectifier R" whose output may be sent through the amplifying tubes at point 30 in the same manner as the output of rectifiers R and In order that the coils 22" shall not, because of their greater inductive capacity, be responsive to surface indications such as burns, flats, etc. I may make their input into rectifier R" less sensitive by means of an adjustable potentiom eter 40.

In Fig. 4 I have disclosed another form of my invention which operates on the same principle of avoiding the small differential between the coils 22 or the coils 22. In this form I eliminate the use of a pair of coils and employ but a single auxiliary coil 23, of larger inductive capacity than coils 22 or 22, instead of a pair of auxiliary coils 22".

This coil will normally cut a constant number of lines of force and no E. M. F. will be generated. When a fissure is encountered, even though it be a large or cracked out fissure with a small variation in the electromagnetic field, coil.

23 will respond thereto to generate an E. M. F. The output of coil 23 may then pass through rectifier R" as before. v r

y In the form of the invention" described in the preceding paragraph variations in the current supply would normally cause a variation in the electro-magnetic field surrounding the rail and would be picked up by coil 23 in the same manner as a fiaw. Where such current variations are likely to occur I may compensate therefor, as shown, by providing a coil 23' connected in opposition and positioned adjacent one of the busbars I I or l2 so that as the current through said bus-bar varies, the E. M. F. generated in coil 23' will be equal and opposite to the E. M. F. generated in coil 23 by variations in current through the rail. The eiIect of such variations is thus eliminated. I

In accordance with the provisions of the patent statutes, I have herein described the principle and operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In a rail flaw detector mechanism adapted for relative movement with respect to the rail, means for sending current through the rail to establish an electromagnetic field surrounding the same, means for detecting flaws in the rail including inductive means positioned with its axis at an angle to the direction of current flow, a similarly positioned auxiliary inductive means of larger inductive capacity than said first means, indicating means, and means whereby said first inductive means and said auxiliary inductive means actuates said indicating means.

2. In a rail flaw detector mechanism adapted for relative movement with respect to the rail, means for sending current through the rail to establish an electromagnetic field surrounding the same, means for detecting flaws in the rail including a pair of opposed induction coils positioned adjacent the rail with their axes'at an angle to the direction of current flow, a similarly positioned auxiliary induction coil of larger inductive capacity than said first coils, indicating means and means whereby said first induction coils and said auxiliary induction coil actuate said indicating means.

3. In 'a rail flaw detector mechanism adapted for relative movement with respect to the rail, means including a bus-bar removed from the rail for sending current through the rail to establish an electromagnetic field surrounding the same, means for detecting flaws in the rail including a pair of opposed induction coils positioned adjacent the rail with their axes at an angle to the direction of current flow, a similarly positioned auxiliary induction coil of larger inductive capacity than said first coils, an induction coil cooperating with said bus-bar and connected in opposition to said auxiliary coil, indicating means and means whereby said first induction coils and said auxiliary induction coil actuate said indicating means.

4. In a rail flaw detector mechanism adapted for relative movement with respect to the rail, means for sending current through the rail to establish an electromagnetic field surroundingthe same, means for detecting flaws in the rail including a pair of opposed induction coils positioned adjacent the rail withtheir axes at an angle to the direction of current flow. a pair of 76 similarly positioned auxiliary induction coils of larger inductive capacity than said first coils, indicating means and means whereby said first induction coils and said auxiliary induction coils actuate said indicating means.

5. In a rail flaw detector mechanism adapted for relative movement with respect to the rail, means for sending current through the rail to establish an electromagnetic field surrounding the same, means for detecting flaws in the rail including a pair of opposed induction coils spaced relatively close together and positioned adjacent the rail with their axes at an angle to the direction of current flow, a pair of similarly positioned auxiliary induction coils spaced relatively further apart than said first coils, indicating means and means whereby said first induction coils and said auxiliary induction coils actuate said indicating means.

6. In a rail fiaw detector mechanism adapted for relative movement with respect to the rail, means for sending current through the rail to establish an electromagnetic field surrounding the same. means for detecting. fiaws in the rail including a pair of opposed induction coils spaced relatively close together and positioned adjacent the rail with their axes at an angle to the direction.

of current flow, a pair of similarly positioned auxiliary induction coils spaced relatively further apart than said first coils and of greater inductive capacity, indicating means and means whereby said first induction coils and said auxiliary induc- 15 tion coils actuate said indicating means.

WALTER M. PERRY. 

